Method for producing highly doped semiconductor components

ABSTRACT

A method is proposed for producing semiconductor components, in which at least one doped region is introduced in a wafer, a solid glass layer provided with dopant being applied on at least one of the two sides of a semiconductor wafer, in another step, the wafer being heated to high temperatures so that the dopant from the glass layer penetrates deep into the wafer to produce the at least one doped region; and in a further step, the glass layer being removed. The method is used for producing homogeneous, heavily doped regions, it also being possible to introduce these regions in the wafer on both sides and for the regions to be of different doping type.

FIELD OF THE INVENTION

The present invention relates to a method for producing semiconductorcomponents.

BACKGROUND INFORMATION

When manufacturing semiconductor components, it is known to producedoped regions in a semiconductor wafer with the aid of ion implantation,gas-phase coating (for example, with diborane or POC13), film diffusionor using liquid solutions.

SUMMARY OF THE INVENTION

In contrast, the method of the present invention has the advantage thatdoped regions with very good homogeneity can be produced. To be regardedas a further advantage is that it is possible, both on the front sideand on the back side of the semiconductor wafer, to introduce suchhomogeneous regions even of different doping types in only one diffusionstep. It is also possible to provide different levels of dopantconcentration on the front side and back side. The heating of the wafer,and with it, the driving of the doping atoms into the interior of thewafer for producing doped regions at high temperatures in the range ofabout 1200 to 1280 degrees Celsius advantageously ensures a deep andconcentrated penetration of the doping atoms into the wafer.

It is particularly advantageous to coat the wafer surfaces with dopingatoms using a chemical vapor deposition method, particularly a chemicalvapor deposition method at atmospheric pressure (APCVD, “AtmosphericPressure Chemical Vapor Deposition”). It is thereby possible to achieveextremely high dopant concentrations which reach up to the solubilitylimit of the silicon wafer.

It is also particularly advantageous to heat the wafer, covered with aglass layer, in oxidizing atmosphere. This advantageously allows thedopant to diffuse into the interior of the wafer in acceptable periodsof time.

Furthermore, it is advantageous to cover the glass layer, provided withdopant, with a neutral glass layer prior to the diffusion process. Amutual influencing of the doping of the front side and back side, or ofdifferent wafers set up in the diffusion oven at the same time, isthereby reliably prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wafer with applied glass layer.

FIG. 2 shows a wafer after a diffusion process.

FIG. 3 shows a wafer after removing the glass layer.

DETAILED DESCRIPTION

FIG. 1 shows a side view of a wire-sawed raw wafer 1 having greatsurface roughness, upon whose front side a p-doped glass layer 2 isapplied, and upon whose back side an n-doped glass layer 4 is applied.Doped glass layers 2 and 4 are covered with a neutral glass layer 3 and5, respectively.

Glass layers 2 and 4 are used for coating the wafer with dopants. Indetail, the production proceeds in the following steps: Raw wafer 1 isfirst of all heated to about 380 degrees Celsius. This is carried out inthat the wafer, in turn with further wafers, is brought on a conveyorbelt into a heating chamber provided with gas injectors. The glass layeris subsequently deposited in an APCVD process (APCVD=“AtmosphericPressure Chemical Vapor Deposition”), thus, a chemical vapor depositionprocess under atmospheric pressure. In so doing, for example, first ofall the front side of the wafer is exposed to a silane gas, in that gasfrom the gas injectors to be passed on the conveyor belt flows onto thesurface of the wafer. In the case of the front side, B2H6 is admixed tothe silane gas. The silane decomposes on the wafer surface heated to 380degrees Celsius and reacts with oxygen to form silicon dioxide. Becauseof the B2H6 admixture, this glass is laced with a p-type dopant. Glasslayer 2 is grown to a layer thickness of about 2 micrometers. Theadmixture of the B2H6 gas has been selected in such a way that the glasslayer has a boron constituent of about 6 percentage by weight. The glasslayer is subsequently exposed to the same silane gas, however, withoutthe addition of B2H6. Neutral glass layer 3 thereby grows on glass layer2. The process is ended when neutral glass layer 3 has a thickness ofabout 0.5 micrometers. In a further step, the wafer is turned over andcorrespondingly coated on the back side with an n-doped glass layer 4(thickness 2 micrometers, phosphorus constituent of about 6 percentageby weight). The n-doping is achieved by admixing PH3 to the silane gasinstead of B2H6. Subsequently, analogous to the front side, a neutralglass layer 5 having a thickness of 0.5 micrometers is applied.

As an alternative to the silane gas method described, the so-called TEOSmethod (TEOS=tetra-ethyl-ortho-silicate) can be used, which can likewiseproceed under normal pressure. In this case, instead of silane gas,Si(OC₂H₅)₄ gas is used, the tetraethyl orthosilicate depositing on thewafer surface decomposing on the surface heated to 380 degrees Celsiusand reacting with oxygen to form silicon dioxide. In this case, thedoping is effected by gas admixture of trimethyl phosphate or trimethylborate.

FIG. 2 shows the wafer after a diffusion process, having a heavilyp-doped region 10 and a heavily n-doped region 11.

The diffusion process, carried out after the coating with doped glasslayers, takes place in a diffusion oven at a temperature of 1200 to 1280degrees Celsius, preferably at a temperature of about 1265 degreesCelsius. A plurality of wafers to be processed simultaneously arearranged upright in a setup made of silicon carbide or polysilicon andhaving retaining elements. This heating is maintained approximately 20to 30 hours, preferably 21 hours, and in particular is carried out inoxidizing atmosphere. With a diffusion time of 21 hours for driving thedopants, stored on the surface in the form of glass layers, into theinterior of the wafer, phosphorus and boron dosages, respectively, ofabout 1-2×10¹⁷ cm⁻² are achieved in regions 10 and 11. This is a dosagehigher by an order of magnitude than for semiconductor applicationsotherwise typical.

In alternative specific embodiments of the diffusion step, it is alsopossible to stack wafers to be processed simultaneously, direct mutualcontact of the wafers being prevented by sprinkling with aluminum oxidepowder beforehand, or by interposing neutral films, known from filmdiffusion.

In a further step, using, for example, 50 percentage hydrofluoric acid,applied glass layers 2, 3, 4 and 5 are removed again, resulting in wafer1 shown in FIG. 3 that is doped on both sides with a heavily p-dopedregion 10 on the front side and a heavily n-doped region 11 on the backside. This wafer can now be used, for instance, for producinghigh-blocking-capability p-n diodes (two-layer diodes) by applying metalcontactings on both sides in further steps. To produce the metalcontactings, for example, metal layers are deposited by sputteringsimultaneously on both sides of the wafer, first of all a chromium layer70 nanometers thick, followed by a nickel-vanadium layer 160 nanometersthick and a silver layer 100 nanometers thick. The wafer is subsequentlydivided along dividing lines into individual diode chips, the dividinglines having optionally already been introduced into the wafer by sawingprior to applying the metal contactings.

The method of the present invention is suitable not only for two-layerdiodes, but can also be utilized in appropriately modified form forproducing multi-layered diodes, particularly diode thyristors(four-layer diodes) and three-layer diodes (transistor diodes). Powersemiconductors, e.g. power diodes, in particular can be easily andreliably produced by the high doping dosages attainable. Thyristors andbipolar transistors can also be produced with the method.

What is claimed is:
 1. A method for producing a semiconductor componentin which at least one doped region is introduced into a semiconductorwafer, comprising the steps of: applying a solid glass layer both on thefront side of the semiconductor wafer and on the back side of thesemiconductor wafer, a doping type of the dopant on the back side beingopposite compared to the doping type of the dopant on the front side;heating the semiconductor wafer to a high temperature of at least 1200degrees centigrade while the glass layer is applied so that the dopantfrom the solid glass layer penetrates into the semiconductor wafer toproduce the at least one doped region; applying a neutral glass layer onthe solid glass layers prior to heating the semiconductor wafer;removing the neutral glass layers together with the solid glass layersafter heating the semiconductor wafer; and providing the dopant at adosage of at least 10¹⁷/cm² in the at least one doped region; whereinthe step of applying the solid glass layer is performed in accordancewith a chemical vapor deposition at atmospheric pressure.
 2. The methodaccording to claim 1, wherein: the step of heating the semiconductorwafer is performed in an oxidizing atmosphere.
 3. The method accordingto claim 1, further comprising the step of: maintaining the hightemperature for about 20 to 30 hours.
 4. The method according to claim1, further comprising the step of: maintaining the high temperature for21 hours.
 5. The method according to claim 1, wherein: the solid glasslayer has a dopant constituent of greater than 2 percentage by weight.6. The method according to claim 1, wherein: the solid glass layer has adopant constituent of about 3 to 6 percentage by weight.
 7. The methodaccording to claim 1, wherein: the solid glass layer has a thickness ofabout 2 micrometers.
 8. The method according to claim 1, wherein: theneutral glass layer has a thickness of about 0.5 micrometers.
 9. Themethod according to claim 1, wherein: the step of removing the solidglass layer is performed in accordance with hydrofluoric acid.
 10. Themethod according to claim 1, wherein the high temperature is between1200 and 1280 degrees centigrade.
 11. A method for producing asemiconductor component in which at least one doped region is introducedinto a semiconductor wafer, comprising: applying a solid glass layerprovided with a dopant on both sides of the semiconductor wafer; heatingthe semiconductor wafer to a high temperature of at least 1200 degreescentigrade while the glass layer is applied so that the dopant from thesolid glass layer penetrates into the semiconductor wafer to produce theat least one doped region; applying a neutral glass layers on the solidglass layer prior to heating the semiconductor wafer; removing theneutral glass layers together with the solid glass layers after heatingthe semiconductor wafer; and providing the dopant at a dosage of atleast 10¹⁷/cm² in the at least one doped region; wherein the solid glasslayer is applied using chemical vapor deposition at atmosphericpressure; and wherein the dopant constituent of the solid glass layer ona front side of the semiconductor wafer is different from the dopantconstituent of the solid glass layer on a back side of the semiconductorwafer.
 12. The method of claim 1, wherein silane gas and B₂H₆ gas isused in the chemical vapor deposition to generate silicon dioxide andp-type dopants.
 13. The method of claim 1, wherein silane PH₃ gas isused in the chemical vapor deposition to generate silicon dioxide andn-type dopants.
 14. The method of claim 1, whereintetra-ethyl-ortho-silicate gas and trimethyl borate is used in thechemical vapor deposition to generate silicon dioxide and p-typedopants.
 15. The method of claim 1, wherein tetra-ethyl-ortho-silicategas and trimethyl phosphate is used in the chemical vapor deposition togenerate silicon dioxide and n-type dopants.
 16. A method for producinga semiconductor component in which at least one doped region isintroduced into a semiconductor wafer, comprising: applying a solidglass layer provided with a dopant on both sides of the semiconductorwafer; heating the semiconductor wafer to a high temperature of at least1200 degrees centigrade while the glass layer is applied so that thedopant from the solid glass layer penetrates into the semiconductorwafer to produce the at least one doped region; applying a neutral glasslayer on the solid glass layers prior to heating the semiconductorwafer; removing the neutral glass layers together with the solid glasslayers after heating the semiconductor wafer; and providing the dopantat a dosage of at least 10¹⁷/cm² in the at least one doped region;wherein the dopant constituent of the solid glass layer on a front sideof the semiconductor wafer is different from the dopant constituent ofthe solid glass layer on a back side of the semiconductor wafer and thesolid glass layer is applied using a chemical vapor deposition atatmospheric pressure using a tetra-ethyl-ortho-silicate gas.
 17. Themethod of claim 16, wherein the neutral glass layer has a thickness ofabout 0.5 micrometers.
 18. The method of claim 16, wherein the hightemperature is between 1200 and 1280 degrees centigrade.